Windowed communication systems using time division multiple access (TDMA) are well known in the art. Multi-carrier communication systems using TDMA are also known. Pursuant to many such systems, an information-bearing signal, such as serial digitized voice or digital data is subdivided into a plurality of bit streams, each of which is encoded into symbols (e.g., 16QAM symbols) to form a corresponding plurality of symbol streams. Synchronization and pilot symbols are inserted into each of the plurality of symbol streams, yielding a plurality of composite symbol streams. The composite symbol streams are used to modulate separate carrier signals, yielding a corresponding plurality of sub-channels each occupying a discrete frequency band and carrying a portion of the information in the original information-bearing signal. The plurality of sub-channels are combined into a composite signal that is transmitted over an RF channel from a first location to a second location.
At the second location, a receiver performs generally the inverse operations, demodulating and detecting each sub-channel separately. Pilot interpolation is performed to determine the carrier's phase and to estimate the effects of channel impairments, such as fading, multi-path effects, etc. Errors may then be corrected to overcome the effect of the channel impairments and to reconstruct the original information signal.
In order to limit the effects of same channel interference in TDMA systems, transmitted signals must be strictly limited to their assigned time slots. This limitation often has unintended consequences in terms of the received symbols.
Accordingly, there is a need for a method of defining synchronization, pilot and data symbols that is useable in multi-carrier communication systems where this time limitation has been implemented. Advantageously, the methodology should define a method of recovery of synchronization, pilot and data symbols for a first number of sub-channels that is applicable to multiple numbers of sub-channels and allows for using similar pilot recovery techniques for any of the sub-channels. The present invention is directed to satisfying or at least partially satisfying these needs.